(1) Field of the Invention
This invention relates to substrate treating apparatus for treating semiconductor wafers, glass substrates for liquid crystal displays, glass substrates for photomasks, and substrates for optical disks (hereinafter called simply “substrates”).
(2) Description of the Related Art
Conventionally, such a substrate treating apparatus is used in a photolithographic process for forming photoresist film on substrates, exposing the substrates having the photoresist film formed thereon, and developing the exposed substrates, as disclosed in Japanese Unexamined Patent Publications Nos. 6-151293 (1994) and 8-17724 (1996), for example).
A conventional substrate treating apparatus includes substrate treating units such as a photoresist forming unit and a developing unit, and an interface unit for transferring substrates between the substrate treating apparatus and an exposing apparatus (stepper) which is an external apparatus. Substrates coated with photoresist are transferred to the exposing apparatus through the interface unit. A chemically amplified photoresist has been used extensively in recent years. This type of photoresist requires a strict control of the time from exposure to heating of substrates in order to maintain high patterning precision. To meet this requirement, the conventional substrate treating apparatus has heating and cooling modules arranged in the interface unit for heating exposed substrates promptly. A substrate returned from the exposing apparatus to the interface unit is promptly loaded into the heating module in the interface unit by a substrate transport mechanism of the interface unit. The substrate heated is then loaded into the cooling module in the interface unit to be cooled to room temperature. The substrate having received post-exposure baking (PEB) treatment in this way is passed from the interface unit to the substrate treating units, and is developed in the developing unit included in the substrate treating units.
The conventional apparatus with such a construction has the following problems (I)-(VI):
Problem (I)
The substrate transport mechanism of the interface unit performs the transport to the post-exposure bake (PEB) described above, besides transport in a forward direction from the photoresist forming unit to the exposing apparatus, and transport in a backward direction from the exposing apparatus to the developing unit. When, for example, substrates are delivered from the exposing apparatus while the interface's transport mechanism is engaged in the transport in the forward direction, the substrates delivered must wait until the transport in the forward direction is finished. As a result, the exposed substrates cannot receive heating treatment promptly.
Problem (II)
In the substrate treating apparatus, a spin chuck and a nozzle usually are in the same positional relationship for each chemical treating unit (e.g. an antireflection film forming unit for forming antireflection film under photoresist film in order to reduce standing wave and halation occurring in time of exposure, and a resist film forming unit). That is, where a nozzle is disposed on the right-hand side of a spin chuck in the antireflection film forming unit, a nozzle is disposed on the right-hand side of a spin chuck also in the resist film forming unit. In this case, a substrate transport mechanism that loads and unloads substrates into/from the antireflection film forming unit could interfere with the nozzle therein, and a substrate transport mechanism that loads and unloads substrates into/from the resist film forming unit could interfere with the nozzle therein.
Problem (III)
An example of heating module has a temporary substrate deposit. This heating module includes, besides a heating plate and the temporary substrate deposit, a holding plate acting as a local transport mechanism. The holding plate is movable to and from the heating plate and temporary substrate deposit, and includes a cooling mechanism. The holding plate receives a substrate heated by the heating plate, cools the substrate with the cooling mechanism while holding the substrate, and then places the substrate in the temporary substrate deposit.
This heating module has the temporary substrate deposit, heating plate and holding plate arranged in a direction perpendicular to a substrate transport path. This arrangement results in unused spaces in the direction perpendicular to directions of transport along the substrate transport path. Where chemical treating modules are stacked in multiple stages, pumps are arranged en bloc on the floor of the apparatus for supplying treating solutions to the chemical treating modules. Thus, the treating solutions are delivered to the chemical treating modules in upper stages as sucked up by the pumps. However, the suck-up action of the pumps may be impaired by viscosity of the treating solutions. It is therefore desirable to provide the pumps for the respective treating modules stacked in multiple stages. However, since space-saving in the perpendicular direction noted above is impossible, the pumps cannot be arranged in multiple stages.
Problem (IV)
An indexer includes a cassette table for receiving cassettes containing substrates to be treated. The substrates to be treated are successively fetched from the cassettes and delivered to the treating units. Treated substrates are successively received from the treating units and deposited in the cassettes. Where substrate rests for transfer of the substrates are provided between the indexer and an adjacent one of the treating units (e.g. an antireflection film forming unit), the substrate rests take up their own installation space.
Problem (V)
As noted in problem (IV) above, an installation space is required for the substrate rests between the indexer and the adjacent treating unit. Such spaces are required also between other adjoining treating units. That is, substrate rests between each adjacent pair of treating units take up their own installation space.
Problem (VI)
In order to cool a substrate, the substrate is moved perpendicular to the substrate transport path (in a direction extending between front and back of the apparatus). The substrate is transferred after heat treatment in a heat-treating module. Cooling modules are often stacked with heating modules, and may therefore be subject to thermal influence.